1. Field of the Invention
The present invention relates to a method for manufacturing a pipe with a partition in such a manner that a partition portion is formed integrally with the middle portion of the pipe.
2. Description of the Related Art
Conventionally, in a heat exchanger such as a capacitor for use in a car or the like, for example, as disclosed in Japanese Utility Model Publication No. Hei. 4-63992, a partition is provided in a header to thereby change a fluid flow passage.
And, conventionally, this type of header with a partition for use in a heat exchanger is manufactured in the following manner as shown in FIG. 25.
At first, an aluminum alloy pipe member with a brazing member clad on the outer surface thereof is cut to a given size to thereby obtain a pipe 11 which can be used in a header.
After then, in the pipe 11, there are formed a tube insertion hole 13, a slit for a divide 15, a fluid flow-in port 17, and a fluid flow-out port 19.
Next, an aluminum alloy divide 21 with brazing members clad on the two surfaces thereof is inserted into the slit for a divide 15, and also two aluminum alloy patches 23 are respectively pressure inserted into the two ends of the pipe 11 so as to manufacture a header pipe.
However, in the thus structured header with a partition for use in a heat exchanger, since there is used an expensive pipe member which has been previously formed in a cylindrical shape, the material cost thereof increases.
Also, there is a fear that a poor brazed condition can occur between the pipe 11 and divide 21.
Conventionally, as a method which has solved these problems, there is known a method for manufacturing a pipe with a partition which is disclosed in Japanese Patent Publication No. Hei. 7-314035.
In this method for manufacturing a pipe with a partition, as shown in FIGS. 26 and 27, there is manufactured a pipe with a partition structured such that a partition portion 33 comprising of a pair of semidivided partition portions 32 is formed in the central portion of a cylindrical-shaped pipe portion 31 thereof.
And, the present pipe with a partition can be manufactured in the following manners:
That is, at first, in a molding step shown in FIG. 28, a plate member formed of aluminum is molded in such a manner that a pair of semidivided cylindrical portions 35 are formed.
The pair of semidivided cylindrical portions 35 are arranged in parallel to each other with an arc-shaped connecting portion 37 between them.
And, each of the paired semidivided cylindrical portions 35 includes a partition forming portion 39 which projects inwardly in a U-shape manner.
Also, each of the paired semidivided cylindrical portions 35 is smaller by 2 mm or so in radius than a pipe portion 31 to be formed, while each semidivided cylindrical portion 35 further includes an edge portion 41 on the outside thereof.
The above-mentioned molding step is carried out by holding a flat plate between a given pair of metal molds and press working the flat plate.
Next, in a cutting step shown in FIG. 29, a portion of the connecting portion 37 situated between the partition forming portions 39, that is, an escape hole 37a, as well as the edge portions 41 respectively situated on the two sides of the partition portions 39 are cut and removed together with the excessively increased thickness portions 41a of the edge portions 41.
This cutting step is executed by trimming and piercing the press worked plate using a press work machinery.
Then, in a compressing step shown in FIG. 30, the partition forming portion 39 is compressed from both sides thereof in a direction of an arrow a in FIG. 30 to thereby form a semidivided partition portion 32.
This compressing step is carried out in such a manner as shown in FIG. 31: that is, the outsides of the semidivided cylindrical portions 35 are respectively held by a work holder 51 which is energized by springs 49 and, on the other hand, two compressing members 53 are respectively disposed on the two sides of the partition forming portion 39 located inwardly of the semidivided cylindrical portions 35, whereby the partition forming portion 39 is compressed and molded by the compressing members 53.
In this compression molding operation, between the compressing members 53, there is interposed a dimension correcting block 55; that is, the inwardly projecting length H of the semidivided partition portion 32 can be corrected by the dimension correcting block 55.
Next, in an edge portion molding step shown in FIG. 32, the two edge portions 41 on the two sides of the pair of semidivided cylindrical portions 35 are molded and, as shown in a lower side in FIG. 32, the edge portions 41 are formed in an arc-shaped manner; that is, the edge portions 41 are so formed as to continue with their respective semidivided cylindrical portions 35 in an arc-shape manner.
This edge portion molding, step is carried out by holding a pair of semidivided cylindrical portions 35 between a given metal molds and then press working them.
Then, in a mutually opposing stop shown in FIG. 33, the connecting portion 37 is projected from the inside thereof to thereby allow the pair of semidivided cylindrical portions 35 to be disposed in such a manner that they are opposed to each other.
In particular, this mutually opposing step is carried out by storing the outsides of the semidivided cylindrical portions 35 into a metal mold 57 and then pressing the connecting portion 37 against the arc portion 61 of the metal mold 57 by a punch 59.
Next, in a butting step shown in FIG. 34, the pair of mutually opposed semidivided cylindrical portions 35 are butted against each other.
This butting step is carried out by storing the outsides of the semidivided cylindrical portions 35 into a metal mold (not shown) and then moving the metal mold. In this step, the semidivided cylindrical portions 35 are molded into a pipe shape.
After then, a connecting step is carried out; that is, not only the pair of semidivided cylindrical portions 35 but also the pair of semidivided partition portions are connected to each other, thereby manufacturing a pipe with a partition which is shown in FIGS. 26 and 27.
The connecting step can be achieved, for example, by executing a brazing operation using non-corrosive flux.
Now, FIG. 35 shows a header with a partition for use in a heat exchanger manufactured in the above-mentioned partitioned pipe manufacturing method; and, the present header with a partition for a heat exchanger includes a partition portion 33 formed in the central portion of a cylindrically-shaped pipe portion 31A thereof.
Also, on one side of the outer periphery of the pipe portion 31A, there are formed tube insertion holes 63 which are spaced from each other at given intervals.
Further, the openings of the pipe portion 31A, which are respectively formed in the two ends of the pipe portion 31A, are closed by cover members 65 respectively.
In the present method for manufacturing a header with a partition for a heat exchanger, after completion of the edge portion molding step shown in FIG. 32, as shown in FIG. 36, the tube insertion holes 63 are formed in one of the semidivided cylindrical portions 35 at given intervals and, at the same time, there are formed a fluid flow-in port 67, into which a thermal medium is allowed to flow, and a fluid flow-out portion 69 from which the thermal medium is allowed to flow out.
This step can be carried out by alit-pierce molding the semidivided cylindrical portion 35 using a press work machinery.
In the thus manufactured header with a partition for a heat exchanger, since a single piece of plate member can be molded easily into a pipe portion 31A having a partition portion 33 formed integrally therewith, there is eliminated the need for use of an expensive pipe member which has been previously formed into a cylindrical shape. This makes it possible to reduce the material cost thereof greatly when compared with the former conventional header.
Also, with use of the present header with a partition for a heat exchanger, when compared with the method in which a pipe is manufactured in a cylindrical shape, since the partition portion thereof is formed integrally with the pipe portion thereof, the number of parts used can be decreased to thereby be able to reduce the cost of the header.
Further, because the tube insertion hole 63 can be worked in a semicircle condition, a mold used to mold the tube insertion hole 63 can be made sufficiently strong, the working time of the tube insertion holes 63 can be shortened, and thus the cost of the header can also be reduced.
However, in the above-mentioned conventional method for manufacturing a pipe with a partition, when the pair of mutually opposed semidivided cylindrical portions 35 are butted against each other to thereby form a pipe shape according to the butting step shown in FIG. 34, actually, as shown in FIG. 37, there is raised a problem that a relatively large gap S is produced between the semidivided partition portion 32 and connecting portion 37.
Such gap S is produced because, in the cutting step shown in FIG. 29, the connecting portion 37 situated between the partition forming portions 39 is cut into a rectangular shape to thereby form the rectangular-shaped escape hole 37a.
That is, if the escape hole 37a is formed in a rectangular shape, after completion of the edge portion molding step following the compressing step shown in FIG. 30, it is assumed that, as shown by dotted lines in FIG. 38, the edge portions of the semidivided partition portions 32 on the connecting portion 37 side thereof are parallel to the center lines of the semidivided cylindrical portions 35.
However, in fact, in the molding step shown in FIG. 28, the reduction of the plate thickness of the partition forming portion 39 on the connecting portion 37 side thereof is smaller than the remaining portions of the partition forming portion 39 and, for this reason, if the partition forming portion 39 is pressed to thereby form the semidivided partition portion 32 according to the compressing step shown in FIG. 30, then the larger plate thickness portions of the partition forming portion 39 on the connecting portion 37 side thereof, as shown in FIG. 38, are caused to project toward the connecting portion 37 side in a trapezoidal manner, so that there are produced projecting portions 32a.
And, if the projecting portions 32a are produced in this manner, then, in the butting step shown in FIG. 34, it is difficult to form the connecting portion 37 in an arc shape and, as shown in FIG. 31, there is formed a relatively large gap S between the semidivided partition portion 32 and connecting portion 37.
By the way, on the opposite side of the semidivided partition portions 32 to the projecting portions 32a, there are formed portions 32b which are parallel to the center line of the semidivided cylindrical portions 35. However, in the butting step shown in FIG. 34, since the edge portions 35a of the semidivided cylindrical portions 35a are deformed and are thereby contacted closely with the portions 32b, there is no possibility that a large gap can be formed in the portions 32b.
Further, according to the above-mentioned conventional partitioned pipe manufacturing method, in the compressing step shown in FIG. 30, as shown in FIG. 39, if the pair of compressing members 53 are pressed against the partition forming portion 39 from the two sides thereof to compress the partition forming portion 39 to thereby form the semidivided partition portion 32, then there is produced a minute gap C1, for example, of the order of 0.05 mm on the outside of the semidivided partition portion 32 and, between the minute gap C1 and the leading end portion 32c of the semidivided partition portion 32, there is produced a relatively large gap C2 of the order of 0.3 mm; that is, there is a fear that, if liquid collects in the gap C2, then the gap C2 portion can be caused to corrode.
It has been found that the cause of production of the gaps C1 and C2; that is, the cause is that, in the molding step shown in FIG. 28, the root portion of the partition forming portion 39 becomes thin in thickness, whereas the leading end portion of the partition forming portion 39 becomes thick in thickness.